The invention relates to a dispenser for releasing flowable media by pressurizing. Particularly liquid media, but also pasty, powdery and/or gaseous media are suitable. The dispenser is held and simultaneously actuated for discharge single-handedly. Most or all parts are injection molded from plastics. The medium may be discharged atomized or delivered in discrete clusters or droplets of a colume of at least 5 or 15 .mu.l and at the most 40 or 25 .mu.l while containing medical active substances for eye treatment, or the like.
Such dispensers need microbiological sealing to prevent the stored medium from germ contamination gaining access from without. The medium is to be protected from such detrimental effects during a long shelf life not only prior to the dispensers first-time use (priming) but also after the initial discharge. The dispenser may be made for a single dose discharge or for moving the actuator only unidirectional without return or suction stroke up to being totally emptied. The total input of medium may be in a single conveying chamber right from the start without provision of any additional medium reservoir. The chamber volume is then variable for pressurized medium delivery. However, the dispenser or its actuator may also operate reversible, namely repeatedly via a working stroke for pressurized delivery directly followed by a return stroke for sucking a further medium dose into the chamber. After discharge of the medium dose the microbiological seal is always to be reproduced until the next discharge. This is not necessary in the case of a disposable dispenser.
For this seal either a single valve or several valves may be suitable. The valves closing gaps sequentially follow within the outlet duct in the flow direction. The last downstream valve is as near as possible to the medium outlet or its bound which is formed by the transition between an inner circumference and a transversely adjoining end face. At this transition the medium detaches from all inner circumferences or inner dispenser surfaces for release to the environment. Downstream thereof the medium may be still guided on external dispenser faces.